Laptop Wont Boot

I have an Advent 6651 and I am unable to get it to boot. I turn it on, the power light comes on, but nothing else, no fan, no screen. After a minute it restarts, with the same effect.

I have removed the battery and unplugged the power, pressed the on button for a minute and then tried again, with no change. I have also reseated the RAM and unplugged the HDD and plugged it back in again.

Has anyone any more suggesstions? Thanks in advance for any help given.